1. Field of the Invention
The present invention relates generally to an automatic plasma processing device. More particularly, the invention relates to a vertical automatic plasma processing device having a vertically disposed plasma generating chamber which, is employed for batch-treatment etching, cleaning, ashing, etc., of workpieces in the form of semiconductor wafers as intermediate products during production of chips having large scale integrated circuits such as LSI's and VLSI's formed thereon.
2. Description of Relevant Art
Fine working in the production of chips having a large scale integrated circuit such as an LSI formed thereon includes a process of etching an insulator film, a semiconductor film or a metal film through a resist film having a fine pattern formed on a semiconductor wafer, another process of cleaning such insulator films, etc., and a further process of ashing to remove the resist film from the surface of the wafer.
Conventionally, the aforesaid processes are effected by a so-called "wet type" processing in which various liquid chemicals such as inorganic acids, organic solvents, etc., are used. However, in addition to the problem of disposition of waste liquids in such processing, working accuracy is also unsatisfactory.
Recently, patterns formed on chips have had a tendency to become finer and finer with the development of VLSI's, and such desired fine patterns cannot be attained by a wet type processing such as described above. Accordingly, various dry type plasma processing devices in which plasma is used have been proposed due to the high working accuracy provided thereby. However, substantially all of such plasma processing devices effect only a processing with plasma, and wafers must be loaded into and unloaded from the plasma generating chamber by manual operations exclusively. For example, wafers are taken out one by one from an unprocessed wafer containing cassette and are transferred one by one to a wafer jig made of quartz or aluminum using a pair of tweezers. Consequently, the percentage of available products is very low due to breaks and cracks of wafers, dropping and contamination of wafers from incomplete clamping of same, etc. Such defects become more material as the diameter of the wafers is increased, e.g., recently to five inches and even to six inches. Further, because the wafers are heated to a high temperature during plasma processing, manual operations to take out the wafers after completion of the processing must be avoided, resulting in an extremely low working efficiency.
In order to eliminate the foregoing disadvantages, devices in which wafers are automatically loaded into a chamber (such as, for example, a device disclosed in Japanese Laid-Open Patent No. 53-90870) have also been proposed. Such devices include a horizontally disposed plasma generating chamber. Because such chamber is elongated in its axial direction, the device cannot be made compact and it is impossible to avoid complicating the structure of the device itself.
The present invention effectively overcomes the foregoing problems attendant the conventional techniques described hereinabove.